Hydrothermal synthesis, characterisation and growth mechanism of Ni(SO4)0.3(OH)1.4 nanowires

A report is presented on the facile fabrication of Ni(SO₄)_0.3(OH)_1.4 nanowires via the hydrothermal synthesis method. The outcome demonstrates that the existence of SO₄^2- and a comparatively lower pH are of great essence to form nanowires morphology rather than flake-like or amorphous ones. When the molar ratio of SO₄^2- to OH^- was 1:1, almost pure nanowires of diameter 20-30 nm and several micrometres long could be obtained. Ni(SO₄)_0.3(OH)_1.4 is actually a type of α-Ni(OH)₂. The growth mechanism of this hydroxyl-lacking hydroxide is discussed. The embedded SO₄^2- between Ni(OH)₂ layers can realise electrostatic equilibrium which may ensure an hcp crystal structure of Ni(OH)₂ having the trend to grow along the (001) direction. On the contrary, when SO₄^2- was superseded by other anions, the nanowires would progressively convert to nanosheets, accompanied by an α-phase to β-phase transformation.